1. Peptide Chemistry Research Center; K. N. Toosi University of Technology; Tehran 15875-4416 Iran
2. Department of Microbiology, Faculty of Biology; University of Tehran; Tehran Iran
3. Organisch Chemisches Institut der Universitaet Heidelberg; Im Neuenheimer Feld 270 Heidelberg 69120 Germany
4. Department of Chemistry; Tarbiat Modares University; Tehran 141115-175 Iran